No, Bitcoin is not legal in your country. I also read about it at this link https://en.wikipedia.org/wiki/Legality_of_bitcoin_by_country_or_territory and it clearly states it is illegal to use bitcoin in Bangladesh .So, I will advice you should only read about this technology and should not invest or indulge in any type of trading related to bitcoin. There are few links which might tell you that even bitcoin mining is legal in Bangladesh but I think even if you earn bitcoin in any ways, there might be no ways for you using it to convert in local currency. But you can use bitcoin to buy stuff online but that too involves high risk as if you get caught you may need to face serious punishment.
Bangladesh is one of the many backward-looking countries we have. The country and its people possess the potential for good economic development but as the way things are life can be a little bit difficult in there. The government must not have an open mind especially on matters like that of cryptocurrency. We just hope that as time goes on there would be new people in the government who can see things the other way around. However, those who are good in computer and can use technologies to hide their tracks can get into Bitcoin or any other cryptocurrency but of course the problem is converting it into cash. Maybe the best way is to have a trusted someone in another country who can convert the Bitcoin into cash and have the cash sent to Bangladesh. I am not also sure if internationally-issued Bitcoin-linked debit cards can work in Bangladesh.